pre-queue filter

I am trying to configure a postfix pre-queue filter. Has anyone
done this and can provide some help? I'm trying to accept
incoming mail, use the pre-queue filter configuration found on
the postfix web site to direct the mail to a third party filter
mechanism, and then pass the mail directly to a second server
(in this case, an Exchange 2003 front-end server). We want the
multi layer effect different servers will give us, but want to
avoid the additional postfix queuing..

Any suggestions? in particular, we have some questions about
passing authentication requests from windows users using POP
clients..

Mossless